Double hydraulic pump with built-in unloading valve



Jan. 2, 19 8 J. J. WOCHQER 3,361,068

DOUBLE HYDRAULIC PUMP WITH BUILTJN UNLOADING VALVE Filed Aug. 18, 1966 United States Patent 3,361,068 DOUBLE HYDRAULIC PUMP WITH BUILT-IN UNLOADING VALVE Joseph J. Wochner, New Berlin, Ill., assignor to Allis- Chalrners Manufacturing Company, Milwaukee, Wis. Filed Aug. 18, 1966, Ser. No. 573,251 6 Claims. (Cl. 103-42) This invention relates to a compact dual pump assembly with built-in unloading means for one of the two pumps.

Heretofore, others have provided or proposed means for unloading one of a pair of pumps driven by a common source; however, such arrangements have not been entirely satisfactory from the standpoint of space requirements, cost and reliability. Characteristically, prior art multiple pump installations with automatic unloading valves have involved use of considerable external piping which is space consuming and expensive. Additionally, the external plumbing is vulnerable to accidental damage and usually requires numerous joints and fittings with attendant sealing problems.

It is an object of this invention to provide an improved multiple pump assembly which has built-in control valve means for unloading one of a pair of pumps in response to the output pressure reaching a predetermined level.

It is a further object of this invention to provide an improved dual pump assembly wherein the housing therefor is comprised of at least three sections, one of which houses a bypass flow control valve for unloading one of the two pumps in the assembly.

It is a further object of this invention to provide a multiple pump assembly having a pair of pumps and a bypass control valve in separate housing sections and wherein a pressure responsive control for the control valve is built into the pump housing to achieve a compact, reliable and readily serviceable unit.

It is a further object of this invention to provide an improved dual pump assembly as hereinbefore outlined having automatic unloading means with reduced hunting characteristics.

These and other objects and advantages of this invention will be apparent to those familiar with the art upon reading the following description in conjunction with the drawing which shows a section view of a dual pump assembly incorporating the invention.

Referring to the drawing, the pump housing 11 includes a first section 12 in which a small capacity gear pump 13 is located, a second section 14 in which a large capacity gear pump 16 is located and a third section 17 in which an unloading type flow control valve 18 is located. The gear pumps 13 and 16 each have one of their two gears connected for rotation to a single shaft 19 which has a splined end 2t] adapted for connection to a rotating power source such as an internal combustion engine. The stacked housing 11 has its sections 12, 14 and 17 and end plate sections rigidly held together by bolts 20. Walls of the housing sections 12, 14 and 17 form an inlet passage 21 interconnecting the inlet side of each of pumps 13, 16. The housing sections also have walls defining an outlet passage 26 which includes a branch passage 27 connected to the outlet side of pump 13 and a branch passage 23 connected to the output side of pump 16. The outlet passage 26 terminates in an opening or outlet 29 which is adapted for suitable connection to a fluid receiving conduit or the like.

A check valve 31 is disposed within section 14 of the pump housing 11 in fluid blocking relation to the branch passage 28. The biasing spring 32 for the check valve 31 is relatively weak and thus does not alford substantial resistance to flow from pump 16 to outlet 29. Pump 16, the larger of the two pumps, is provided with a bypass passage 36 interconnecting its input and output sides.

3,361,068 Patented Jan. 2, 1968 The bypass passage 36 is partly in section 14 and partly in section 17 of the pump housing, thus permitting the flow control valve 18 to be located in the intermediate section 17.

Valve component 59 of control valve 18 is shifted by operation of pressure responsive means from its illustrated closed position, wherein fluid flow in bypass 36 is blocked, to an open position, in which fluid flow from the output to input side of pump 16 through bypass passage 36 is permitted. The pressure responsive means for shifting flow control valve 18 includes a pressure sensitive pilot valve 41 and an actuator mechanism 42 associated therewith. The operation of the flow control valve 18, pilot valve 41 and actuator mechanism 42 will be more apparent from the following description of the operation of the pump assembly.

When both pumps 13 and 16 deliver their output to the outlet 29, the pressures in branch passages 27, 28 of the outlet passage 26 are essentially the same. In this condition of operation, the pressure chamber 56 is at the same pressure as outlet branch 28 and plunger 43 of actuator mechanism 42 is balanced due to exposure at both its ends to substantially the same fluid pressure.

When the pressure in the branch passage 28 reaches a predetermined high value, the pilot valve 41, acting in a manner similar to a pressure relief valve, opens, thus allowing high pressure fluid in cylindrical chamber 56 to escape to the inlet passage 21 through a dumping passage comprising chamber 62, the opening in valve seat 52 and openings 50 in retainer 45. This permits the pressure in chamber 56 to drop, since bleed hole 57 in how control valve 18 does not permit enough fluid flow to maintain a high pressure in the chamber 56. The output pressure of branch 28 acts, through the bypass passage 36, against the conical surface 58 of the valve member 59 and the resulting force will be suflicient to shift the component 59 to the left against the action of spring 65 off its seat 63, to its open position thereby permitting flow through the bypass passage 36 to the inlet side of the pump 16. Simultaneously, the plunger 43 becomes unbalanced since its end 60 in chamber 46 is exposed to the high output pressure of the outlet passage 26, through its connecting passage 66 to branch outlet passage 27, while its opposite end 61 is exposed to the decreased pressure of chamber 62, which is in free flow fluid communication with chamber 56 and together may be considered a single chamber. The plunger 43 in its unbalanced condition acts against valve element 51 of pilot valve 41 and serves to keep the latter open until the pressure in output passage 26 falls below the opening pressure for valve 411 a predetermined value.

The built-in control system for the two pumps 13, 16 is designed to achieve opening of the bypass for pump 16 when the pressure of the outlet branch 28 reaches a predetermined value and closing of the bypass at a substantially lower pressure. The diameter of plunger 43 is slightly greater than the diameter of bore 64 and thus plunger end 60 has a greater effective pressure area than the valve element 51. With this proportioning of components of the pressure responsive means, the pilot valve 41 will not be permitted to close until the fluid pressure in outlet branch 27 falls below its opening pressure a substantial predetermined value. This obviates hunting action of the pilot valve 41. The hunting action referred to is relatively rapid cyclic opening and closing of the valve upon minor fluctuations in pressure. Such hunting action tends to pound out the valve seat causing annoying noise. It should be understood that as the pilot valve 41 opens and closes, the control valve also opens and closes and thus hunting action of the pilot valve causes hunting action of the control valve.

The embodiments of the invention in which an exclusive property or priviledge is claimed are defined as follows:

1. A multiple pump assembly comprising:

a stacked housing including first and second sections each having a pump therein and a third section disposed between said first and second sections,

an inlet passage in said housing interconnecting the input sides of said pumps,

an outlet passage in said housing having an outlet and first and second branches connected to the output sides of said pumps, respectively,

a check valve in one of said branches permitting flow of fluid from one of said pumps to said outlet and preventing reverse flow,

a bypass passage in said housing interconnecting the input and output sides of said one pump including a portion in said third section,

a flow control valve in said third section shiftable between a closed position in which fluid flow in said bypass passage is blocked, and an open position in which fluid flow through said bypass passage is permitted,

resilient biasing means urging said control valve toward its closed position, and

pressure responsive means in said housing for causing said control valve to be shifted from its closed position to its open position in response to the fluid pressure in said one branch exceeding a predetermined pressure.

2. The assembly of claim 1 wherein said pressure responsive means maintains said control valve in its open position, once it is opened, until the fluid pressure in said other branch falls below said predetermined pressure a substantial predetermined value.

3. The assembly of claim 1 wherein said control valve is reciprocally disposed in a pressure chamber which when pressurized urges said control valve toward its closed position, wherein said pressure responisve means includes a restricted flow passage placing said pressure chamber in fluid communication with the output side of said one pump, a dumping passage in said housing interconnecting said pressure chamber and said inlet passage, a pilot valve in said housing including a control element having a closed position in which flow through said dumping assage is prevented and an open position in which fluid flow through said dumping passage is permitted, means resiliently biasing said pilot valve toward its closed position, and actuating means sensitive to fluid pressure in said other branch for holding said pilot valve in its open position once it is opened until the fluid pressure in said other branch falls below said predetermined pressure a predetermined value.

4. The structure set forth in claim 3 wherein said actuating means includes walls in said housing defining a cylinder having fluid compartments at its opposite ends, passage means in said housing placing said compartments in fluid communication with said pressure chamber and other branch, respectively, and a plunger in said cylinder having an end in confronting relation to said control elernent of said pilot valve.

5. The structure set forth in claim 4 wherein said check valve is in one of said first and second sections and said pilot valve and plunger are in one of said second and third sections.

6. The structure set forth in claim 4 wherein the effective pressure area of said plunger is greater than the effective pressure area of said control element of said pilot valve exposed to the pressure of said pressure chamber.

References Cited UNITED STATES PATENTS 3,021,790 2/1962 Brunson 10342 3,146,717 9/1964 Tyree 103-5 3,147,712 9/1964 Gaubatz 103-42 X 3,150,593 9/1964 Funk et a1. 103-42 X 3,162,129 12/1964 Erikson 103-126 X 3,184,151 5/1965 Shaw 230-31 3,198,120 8/1965 Little 103-5 3,233,651 2/1966 Smith 10342 X 3,266,426 8/1966 Brunson 103-42 3,291,052 12/1966 Weaver et al. 103--5 DONLEY J. STOCKING, Primary Examiner.

W. I. KRAUSS, Assistant Examiner. 

1. A MULTIPLE PUMP ASSEMBLY COMPRISING: A STACKED HOUSING INCLUDING FIRST AND SECOND SECTIONS EACH HAVING A PUMP THEREIN AND A THIRD SECTION DISPOSED BETWEEN SAID FIRST AND SECOND SECTIONS, AN INLET PASSAGE IN SAID HOUSING HAVING AN OUTLET AND INPUT SIDES OF SAID PUMPS, AN OUTLET PASSAGE IN SAID HOUSING HAVING AN OUTLET AND FIRST ANS SECOND BRANCHES CONNECTED TO THE OUTPUT SIDES OF SAID PUMPS, RESPECTIVELY, A CHECK VALVE IN ONE OF SAID BRANCHES PERMITTING FLOW OF FLUID FROM ONE OF SAID PUMPS TO SAID OUTLET AND PREVENTING REVERSE FLOW, A BYPASS PASSAGE IN SAID HOUSING INTERCONNECTING THE INPUT AND OUTPUT SIDES OF SAID ONE PUMP INCLUDING A PORTION IN SAID THIRD SECTION, A FLOW CONTROL VALVE IN SAID THIRD SECTION SHIFTABLE BETWEEN A CLOSED POSITION IN WHICH FLUID FLOW IN SAID BY PASS PASSAGE IS BLOCKED, AND AN OPEN POSITION IN WHICH FLUID FLOW THROUGH SAID BYPASS IS PERMITTED, RESILIENT BIASING MEANS URGING SAID CONTROL VALVE TOWARD ITS CLOSED POSITION, AND PRESSURE RESPONSIVE MEANS IN SAID HOUSING FOR CAUSING SAID CONTROL VALVE TO BE SHIFTED FROM ITS CLOSED POSI TION TO ITS OPEN POSITION IN RESPONSE TO THE FLUID PRESSURE IS SAID ONE BRANCH EXCEEDING A PREDETERMINED PRESSURE. 